Iterate through an html string to find all img tags and replace the src attribute values

Question

I have an html code as a string. I need to find all img tags in that string, read the value of each src attribute and pass it to a function, that function returns an entire

Answer 1

If I understand your need correctly you can use HtmlAgilityPack for this purpose. Using regex may cause unwanted behavior. Can you try the code below ?

public static string DoIt()
{
        string htmlString = "";
        using (WebClient client = new WebClient())
            htmlString = client.DownloadString("http://dean.edwards.name/my/base64-ie.html"); //This is an example source for base64 img src, you can change this directly to your source.

        HtmlDocument document = new HtmlDocument();
        document.LoadHtml(htmlString);
        document.DocumentNode.Descendants("img")
                            .Where(e =>
                            {
                                string src = e.GetAttributeValue("src", null) ?? "";
                                return !string.IsNullOrEmpty(src) && src.StartsWith("data:image");
                            })
                            .ToList()
                            .ForEach(x =>
                            {
                                string currentSrcValue = x.GetAttributeValue("src", null);
                                currentSrcValue = currentSrcValue.Split(',')[1];//Base64 part of string
                                byte[] imageData = Convert.FromBase64String(currentSrcValue);
                                string contentId = Guid.NewGuid().ToString();
                                LinkedResource inline = new LinkedResource(new MemoryStream(imageData), "image/jpeg");
                                inline.ContentId = contentId;
                                inline.TransferEncoding = TransferEncoding.Base64;

                                x.SetAttributeValue("src", "cid:" + inline.ContentId);
                            });


        string result = document.DocumentNode.OuterHtml;
}

You can retrieve HtmlAgilityPack from https://www.nuget.org/packages/HtmlAgilityPack

Hope this helps